How to pass C# object model as type to postgresql function by dapper

Question

I'm trying to pass C# object model as postgresql type to function by dapper but I get this error:

System.NotSupportedException: The CLR type System.Data.DataTable isn't natively supported by Npgsql or your PostgreSQL. To use it with a PostgreSQL composite you need to specify DataTypeName or to map it, please refer to the documentation.

My postgresql type is image with url property.

This is my function in postgresql:

CREATE OR REPLACE FUNCTION public.createapp(applicationid text, images image)
    RETURNS void
    LANGUAGE 'plpgsql'
AS $BODY$
BEGIN
    INSERT INTO app 
                     (
                         id,
                         applicationid,
                         images
                     )
                VALUES
                    (
                         uuid_generate_v4(),
                         applicationid,
                         images
                    );
    
END
$BODY$;

My image model is:

public class Image
{
    public string Url { get; set; }
}

And this is my C# Dapper repository code:

var parameters = new DynamicParameters();
parameters.Add("applicationid", application.ApplicationId);
parameters.Add("images", application.Images);
var result = await GetDb().QueryFirstOrDefaultAsync("createapp", parameters, commandType: CommandType.StoredProcedure);

How can I pass this parameter to my function?

Answer 1

you need to register your custome type in startup like this:

SqlMapper.AddTypeHandler(new PgTypeHandler<SomeType>());

and then define your type in sql script parameter like this: @images::sometype

internal class PgTypeHandler<T> : SqlMapper.TypeHandler<T>
    {
        public override T Parse(object value)
        {
            return (T)value;
        }

        public override void SetValue(IDbDataParameter parameter, T value)
        {
            parameter.Value = value;
        }
    }

more document: https://www.npgsql.org/doc/

Answer 2

I solved this by add MapComposite in startup.cs:

NpgsqlConnection.GlobalTypeMapper.MapComposite<Model.Entities.Image>("image");

That "image" is my postgresql type.